JP2507758B2 - Method for producing polyester - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a polyester, and more particularly to a method for producing a thermotropic liquid crystalline polyester having a high intrinsic viscosity in a short time. is there.

(Prior Art) Polyester has been widely accepted as a general molded article, but many polyesters have insufficient mechanical properties such as flexural strength and flexural modulus. Therefore, it was not suitable for fields requiring high physical properties.

In recent years, there has been an increasing demand for materials having excellent strength, rigidity, heat resistance and chemical resistance, regardless of whether they are fibers, films or molded products.

Already, as a pioneer of polyester with such high physical properties, WJ Jackson has been
-Thermotropic liquid crystalline polyester composed of -hydroxybenzoic acid has been reported, and attention has been paid to such thermotropic liquid crystalline polyester. This thermotropic liquid crystalline polyester has mechanical properties that are several times higher than those of ordinary polyesters that do not exhibit thermotropic liquid crystalline properties, and we have found a new possibility for highly functional polymers.

Generally, this thermotropic liquid crystalline polyester is produced by adding polyethylene terephthalate to
-It is produced by contacting with acetoxybenzoic acid to cause an acidolysis reaction, and then performing a polycondensation reaction in the second step. However, this manufacturing method has the following drawbacks. That is, the polycondensation rate in the second step is slow.

It is difficult to produce polyesters with high intrinsic viscosity.

This is because when the acidolysis reaction of polyethylene terephthalate with 4-acetoxybenzoic acid is carried out, as a result, some of the hydroxyl residues of ethylene glycol are acetated, resulting in significant inactivation, or scattering out of the system. So, after all, for all carboxyl groups,
There was a problem that the amount of all hydroxyl groups was insufficient, and as a result, the polycondensation rate was slowed or a polyester having a high intrinsic viscosity could not be obtained.

Various measures have been proposed to solve these problems. For example, JP-A-60-186525 discloses a method of reacting 4-acyloxybenzoic acid and polyalkylene terephthalate in the presence of acetic anhydride.
This method also had an insufficient improvement effect.

(Problems to be Solved by the Invention) As described above, in the prior art, although the productivity can be improved to some extent, there remains a problem that the resulting polyester has a low intrinsic viscosity. It was

An object of the present invention is to provide a method for producing a thermotropic liquid crystalline polyester which has a high intrinsic viscosity and which is particularly suitable for fibers, films and other molded articles in a short time.

(Means for Solving Problems) The inventors of the present invention have conducted extensive studies to provide a method for producing a thermotropic liquid crystalline polyester that does not have the above problems, and as a result, have found that bis- (β) as an ethylene terephthalate component. -Hydroxyethyl) terephthalate or its low polymer is mixed with a specific amount of ethylene glycol, and then with 4-acyloxybenzoic acid component.
The present invention has been accomplished by finding that the above object can be achieved.

That is, the present invention provides a 4-acyloxybenzoic acid component,
In producing a thermotropic liquid crystalline polyester from a polyester component containing ethylene terephthalate as a main constituent, bis- (β-hydroxyethyl) terephthalate or its low polymer is used in an amount of 1/20 to 1 of the equivalent number of all terminal groups. A method for producing a thermotropic liquid crystalline polyester having an intrinsic viscosity of at least 0.5 is characterized in that it is mixed with a double equivalent of ethylene glycol and then with a 4-acyloxybenzoic acid component, and then polycondensation is completed. It is what

The thermotropic liquid crystalline polyester produced by the method of the present invention has an intrinsic viscosity of at least 0.5, preferably
0.5-1.0, optimally 0.6-0.8. Unless the intrinsic viscosity is 0.5 or more, various physical properties such as Izod impact strength,
Inferior mechanical properties.

The thermotropic liquid crystallinity referred to in the present invention refers to the property that molecules are regularly arranged in a certain direction in the molten phase, and can be confirmed by a conventional deflection technique.

Used in the production of polyester in the present invention 4-
As the acyloxybenzoic acid component, it is basically necessary to select a para-oriented compound because it plays a role in the rigid portion of the thermotropic liquid crystalline polyester. Examples of such compounds include 4-hydroxybenzoic acid, 4-hydroxy-3-methylbenzoic acid, 4-hydroxy-3-chlorobenzoic acid acetates, propionates, butyrates and isopropionates. Examples include esters and α, α-dimethylpropionate, with 4-acetoxybenzoic acid being the most suitable. In addition, as long as the liquid crystallinity of the resulting polyester is not impaired, it is possible to add and copolymerize each of the orientation compounds of amphi, ortho, meta, ana, epi, cata, peri, and pros simultaneously with the para orientation compound. it can.

In the present invention, as the polyester component mainly composed of ethylene terephthalate used in the production of polyester in the present invention, bis- (β-hydroxyethyl) terephthalate and / or its known synthetic esterification method or transesterification method can be used. It is a low polymer (BHET).

In the method of the present invention, BHET is used in an amount not exceeding the equivalent number of all the end groups, that is, 1/20 to 1 times equivalent, and optimally 1/6 to 1/2 times equivalent of ethylene glycol. After mixing, it is necessary to mix with 4-acyloxybenzoic acid component and then complete polycondensation. If the amount of ethylene glycol added exceeds the number of equivalents of all the end groups of BHET, the polycondensation rate will rather decrease, or the diethylene glycol bond concentration will increase, and the heat resistance of the resulting polyester will decrease, which is preferable. Absent. On the other hand, in order to substantially bring out the effect of adding ethylene glycol, it is necessary to add 1/20 equivalent of the equivalent number of all end groups of BHET.

The equivalent number of all end groups of BHET is 1,400 to 1,800 equivalent / ton-BHET when the intrinsic viscosity is 0.1 and 600 when the intrinsic viscosity is 0.2.
It is about 700 equivalents / ton-BHET.

The 4-acyloxybenzoic acid component added to BHET has a molar ratio of repeating units to the ethylene terephthalate component of preferably 50:50 to 95: 5, particularly preferably 50:50 to 80:20.
The content is appropriately selected and added within the range.

In the method of the present invention, it is preferable to add a small amount of an acid anhydride of a lower fatty acid to cause a reaction so that the polycondensation rate can be accelerated.

As an acid anhydride of a lower fatty acid that can be preferably used,
Acid anhydrides of lower fatty acids having 1 to 8 carbon atoms, such as acetic anhydride, propionic anhydride, monochloroacetic anhydride, dichloroacetic anhydride, trichloroacetic anhydride, monobromoacetic anhydride, dibromoacetic anhydride, tribromoacetic anhydride, monofluoroanhydride Acetic acid, difluoroacetic anhydride, trifluoroacetic anhydride, bromoacetic anhydride, glutaric anhydride, maleic anhydride, succinic anhydride, β-bromopropionic anhydride, butyric anhydride, isobutyric anhydride, propylacetic anhydride, valeric anhydride,
Pivalic anhydride and the like can be mentioned, but acetic anhydride is particularly preferably used in terms of price and boiling point.

In addition, in the present invention, for example, 2,2-bis (4'-hydroxyphenyl) propane, hydroquinone, resorcin, 4,4'-, as long as the object of the present invention is not impaired.
Dihydroxydiphenyl, 1,4-butanediol, 2-butene-1,4-diol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, pentaerythritol, 2,6-
Naphthalenedicarboxylic acid, isophthalic acid, phthalic acid, adipic acid, sebacic acid, 2,2-bis (4'-carboxyphenyl) propane, bis (4-carboxyphenyl) methane, bis (4-carboxyphenyl) ether, trimellit An acid, 2-hydroxy-6-naphthoic acid or the like can be copolymerized.

In the present invention, the reactor is charged with a predetermined amount of BHET,
Reaction schedules (a), (b), (c), which will be described later,
It is preferable to react in the order of (d).

First, (a) ethylene glycol is added in an inert atmosphere, and the reaction is performed at a temperature not exceeding 250 ° C for 30 minutes to 4 hours. When the temperature exceeds 250 ° C, ethylene glycol is scattered, and when the reaction time is less than 30 minutes, the reaction becomes insufficient and the reaction rate in the polycondensation step may become slow, which is not preferable. On the other hand, even if the reaction is carried out for 4 hours or more, the effect will be saturated, which is also economically unfavorable.

Then, (b) 4-acyloxybenzoic acid (preferably at the same time, 0.01 to 0.25 times equivalent of acetic anhydride equivalent to hydroxyl residue of 4-acyloxybenzoic acid) is added at a temperature not exceeding 250 ° C. Allow to react for 30 minutes to 8 hours. If the temperature rise time exceeds 8 hours or the temperature exceeds 250 ° C, 4-acyloxybenzoic acid (and / or acetic anhydride) may be scattered, which is not preferable.

Thereafter, (c) the temperature is raised to 250 ° C to 320 ° C, and when the temperature reaches 270 ° C at the latest, decompression for 60 minutes or more, preferably 80 to 120 minutes until full vacuum is reached. Start decompression on a schedule. Temperature is 320
If the temperature exceeds ℃, the color tone of the resulting polyester will be impaired. If the decompression schedule is less than 60 minutes, 4-acyloxybenzoic acid may be scattered, which is also not preferable.

After that, (d) usually at a temperature of 250 to 320 ° C., under a high reduced pressure of about 1 torr, for several tens of minutes to several hours, while acetic acid is distilled in the molten phase, a polycondensation reaction is carried out to obtain the objective Polyester can be produced.

Usually, a catalyst is used in the polycondensation reaction, but when the polyester is produced by the method of the present invention, various metal compounds or organic sulfonic acid compounds can be used as the catalyst.

Examples of such metal compounds include compounds such as antimony, titanium, germanium, tin, zinc, aluminum, magnesium, calcium, manganese, sodium, potassium, and cobalt, and examples of organic sulfonic acid compounds include sulfosalicylic acid and o-sulfobenzoic acid. Compounds such as acid anhydrides are used, but antimony trioxide and o
-Sulfobenzoic anhydride is particularly preferably used. The amount of catalyst added is usually 0.1 × 10 ^{-4 to} 100 × 10 ^-4 mol, preferably 0.5 × 10 ^-4 , per 1 mol of the polyester repeating unit.
˜50 × 10 ⁻⁴ mol, optimally 1 × 10 ⁻⁴ to 10 × 10 ⁻⁴ mol.

The thermal characteristics of the polyester obtained by the method of the present invention include a melting point of 200 ° C or higher, a heat distortion temperature of 60 ° C or higher, preferably a melting point of 240 ° C or higher, a heat distortion temperature of 120 ° C or higher, and most preferably a melting point.
A temperature of 250 to 300 ° C and a heat distortion temperature of 150 to 200 ° C are suitable in terms of achieving both heat resistance and various physical and mechanical property values.

(Function) Although the reason why a polyester having a high intrinsic viscosity can be produced in a short time by the method of the present invention is not fully understood, an amount of ethylene glycol which does not exceed the equivalent number of all end groups of BHET is obtained. Since ethylene and a polyester having ethylene terephthalate as a main component are preliminarily reacted with each other, the ethylene glycol component is present in a proper excess, and ethylene glycol becomes an acetate body with low reactivity, or ethylene glycol becomes ethylene glycol. It may scatter itself or as acetate or diacetate of ethylene glycol, and even if a part of it is discharged out of the system, the balance between the carboxyl group and the hydroxyl group may be lost, or the reaction rate may decrease. It is presumed that it is because there is no.

(Example) Hereinafter, the present invention will be described in more detail with reference to examples.

 In the examples, the characteristic values of polymers were measured by the following methods.

Intrinsic viscosity [η] in a mixed solvent of equal weight of phenol and ethane tetrachloride at 20 ℃
It was determined from the solution viscosity measured in.

All end groups were calculated back from the value of intrinsic viscosity.

Melting point Tm The temperature was measured with a differential scanning calorimeter (DSC-2 type manufactured by Perkin Elmer Co., Ltd.) at a heating rate of 20 ° C./min.

Flow starting temperature Tf Using a flow tester (CFT-500 type manufactured by Shimadzu Corporation),
Initial temperature 200 ℃ under the condition of load 100Kg / cm ² and nozzle diameter 0.5mm
The temperature was raised at a rate of 10 ° C / min, and the temperature was determined as the temperature at which the polymer started to flow out from the die.

The thermotropic liquid crystallinity was confirmed with a Leitz polarization microscope with a hot stage.

Example 1 A mixture of bis- (β-hydroxyethyl) terephthalate obtained by a known method and its low polymer (hereinafter referred to as an oligomer. Intrinsic viscosity 0.1: equivalent number of all terminal groups 1,600 equivalent / to)
n-oligomer) and ethylene glycol 1,000 equivalents / ton-
The oligomer was charged into the reactor and mixed by stirring at 230 ° C. for 1 hour. Then, under normal pressure, 6 mol of 4-acetoxybenzoic acid and 0.9 mol of acetic anhydride with respect to 4 mol of the oligomer (0.15 times equivalent to the hydroxyl residue of 4-acetoxybenzoic acid)
Then, 2 × 10 ⁻⁴ mol of antimony trioxide was added to 1 mol of all acid components of the polyester, and the temperature once lowered was raised to 270 ° C. over 5 hours.

After that, decompression was started according to a decompression schedule such that it took 90 minutes to reach full vacuum. Finally at a temperature of 270 ° C,
As a result of polycondensation reaction in the melt phase for 4 hours under a reduced pressure of 0.3 torr, a thermotropic liquid crystalline polyester having [η] 0.73 and Tf 189 ° C was obtained.

Examples 2 to 4 and Comparative Examples 1 to 2 Thermotropic liquid crystalline polyesters were obtained by reacting in substantially the same manner as in Example 1 except that the addition amount of ethylene glycol was changed variously as shown in Table 1.

 The results are shown in Table 1.

As is clear from Table 1, in Comparative Example 1, Tf was 147 ° C.
In Comparative Example 2, the polycondensation time was as slow as 10 hours, which was not preferable.

Examples 5-7 Example 1 except that the molar ratio of 4-acetoxybenzoic acid to ethylene terephthalate units was 5: 5, 7: 3 or 8: 2.
The reaction was carried out in the same manner as above to obtain a thermotropic liquid crystalline polyester.

 The results are shown in Table 1.

(Effects of the Invention) According to the present invention, a thermotropic liquid crystalline polyester having a high intrinsic viscosity can be obtained in a short time. Also,
The thermotropic liquid crystalline polyester obtained by the present invention is extremely useful as a material used for applications requiring particularly high physical properties.

Continuation of front page (56) References JP-A-60-186526 (JP, A) JP-A-62-41220 (JP, A) JP-A-61-12726 (JP, A) JP-A-63-278928 (JP , A) JP-A 63-30523 (JP, A) JP-A 64-33123 (JP, A)

Claims (1)

(57) [Claims] 1. When producing a thermotropic liquid crystalline polyester from a 4-acyloxybenzoic acid component and a polyester component containing ethylene terephthalate as a main constituent, bis- (β-hydroxyethyl) terephthalate or a low polymer thereof is used. 1/20 of the equivalent number of all the terminal groups
A method for producing a thermotropic liquid crystalline polyester having an intrinsic viscosity of at least 0.5, which comprises mixing 1-fold equivalent amount of ethylene glycol, then mixing with 4-acyloxybenzoic acid component, and then completing polycondensation.